Variable resistors



Se t. 3, 1963 1.. A. SIELSCH VARIABLE RESISTORS Filed Oct. 25. 1960 IN VEN TOR [E0 .1, 157515 ATTORNEY Filed Oct. 25, 1960, Ser. No. 64,874 8 Claims. (Cl. 338-454) United States Patent My invention relates to electric measuring instruments,

and more particularly relates to a variable electric resistor. As a principal use of such an instrument is asa potentiometer, such an embodiment of my invention will be herein described, although there are other uses to which it may begput. Also, although herein shown and described as a rotary potentiometer, it Will'be at once apparent to those skilled in the art that it may be constructed and used as a translatory instrument.

An object of my invention is to provide an electric resistor having its operating parts sealed in an'oil bath of minimum size. While there have been numerous resistors heretofore which have operated in oil, they have been cumbersome, heavy, unnecessarily large, and difficult to seal, being usually entirely contained in an oil bath,'the bulk of which served no useful purpose.

Another object of my invention is to provide an electric resistor in which temperatures generated in the resistance element are at once-conducted away and dissipated by means of the bath and the intimate association of the bath with both the resistance element and the travelling element. v

Other objects of my-invention include provision of an electric resistor which has a low noise level, a high power rating, low torque, and a minimum of variation of electrical characteristics over its entire life. V

In the accompanying drawing illustrative of a presently preferred type of potentiometer, but not intended to eX- elude instruments of the translatory type, FIG. 1 is a diametrical sectional view showing the assemblage of elements in a rotary annular instrument;

. -FIG. 2 is a sectional'view onthe' line 2--2 of FIG. 1,

.arm andthe ball contained thereby; and

FIG. 5 is a schematic diagram of the circuitry.

Having reference now to the details of the drawing, I have shown in FIG. 1 a housing having a cup-shaped member 11 and a cap 12, held together and sealed by a clamp ring 14. A rotatable shaft 15'extends through a bearing 16 in the cup member 11 and is supported at its inner end 17 by a bearing 18 in the cap 12. A drum 19,

on the shaft 15 supports a slider arm Ztl which is ofleaf spring material.

3,102,989 Patented Sept. 3, 1963 "ice is an annular flexible electroconductive tape 29, in spaced overlying relationship to the mandrel 24 and the resistance element 25 wound thereon. Obviously the tape 29 may be combined with the diap-hragm 28 by suitable changes in conductivity and insulating properties, rather than being secured to the diaphragm as a separate element;

The spring leaf slider arm has at its end 30* a-flange 31, preferably toroidal, secured as by welding to the face of the arm 20 adjacent to the diaphragm 28. A ball 32 is disposed in contact with the resistance element and under the diaphragm 28 and tape 29 and within the cavity 33 defined by the flange 31. When the arm 20* is moved, the flange 31 moves easily over the fluid-supported diaphragm 28, depressing the diaphragm into the groove 22. The ball 32 is pushed outward by the mandrel 24 and resistance element 25 into the cavity 33 within the flange 3 1,

. the diaphragm 28 and tape 29 yielding to form a pocket 34 in which the ball 32 is confined. Thus, as the arm 20 sweeps the circle of the potentiometer, the ball 32 is moved by the flange 3'1 and the pocket 34, from which the ball cannot escape, in contact with both the resistance element 25 and the conductive tape 29.

Suitable terminals 35 are provided for completing the requisite circuits in the ordinary manner of such instruments. The tape 29 is connected to one such terminal as shown in FIG. 5, the circuit wire 36 being spot welded to the tape. The resistance element 25 is also connected to terminal 35 by a wire 37.

It will be seen that the ball 32 has the function of the usual slider, but instead of being a rigid part of a slider arm or even being nested in a metallic socket on the slider arm, theball 32 is nested in a movable pocket in the flex filled groove 22. The usual slip ring on the movable arm In a recessed shoulder 21 in the cup member 11, and

facing toward the cap 12 is annular groove 22 (see FIG. 3). Within the groove 22 is an annular mandrel 24 upon which the resistance element 25 is supported. The mandrel 24 has one flat face 26, and resistance element 25, which may be a wire coil, is flattened correspondingly as it crosses the face 26, to provide a suitable track'for a slider or brush element. The groove 22 is filled with a fluid lubricant 27. The lubricant 27 is held sealed in the groove 22 by an. annular flexible diaphragm 28,. preferably of insulating material, which maybe heat-pressed upon the shoulder 21 to secure it thereto. The diaphragm 2t is spaced from the resistance element 25 which liesentirely within the groove 22 and below the shoulder 21. Secured to the under side of thediaphragm-that is, the

is replaced by the tape slip ring 29 which, like the ball 32 and resistance element 25, is within the groove. All these elements are cooled by the lubricant 27 which is heat-conductive but not electro-conductive.

The disclosed embodiment is not to be construed as a limitation upon my invention, the scope of which is deemed to include any desirable constructive modification within the spirit and breadth of the appended claims.

I claim:

1. A variable resistor comprising housing means, a resistance element carried by said housing means, a flexible diaphragm attached to said housing means overlaying said resistance element and spaced therefrom so as to enclose said resistance element, an electro-conductive ball mounted for rolling between said resistance element and said diaphragm, an arm mounted on said housing means for movement of its free end over said diaphragm on the side of said diaphragm opposite to said ball and parallel to said resistance element, a flange on the free end of said arm defining a cavity within said flange, said flange pressing said diaphragm uponsaid ball to form a pocket confining said ball whereby upon movement of said arm said ball and arm are constrained to move as a unit having relative motion with respect to said resistance element and said diaphragm, an electric circuit connected to said resistance element, and a second electric circuit with which said ball is in circuit. 2 i

2. A variable resistor as set forth in claim 1, in which said housing means defines a groove containing said resistance element and said ball, said flexible diaphragm being sealed to said housing means over said groove, and said groove containing a fluid lubricant.

3. A variable resistor as set forth in claim 1, in which said arm includes resilient means for maintaining said member pressed against said diaphragm.

4. A variable resistor comprising housing means having a groove, aresistance element within said groove,

an electro-conductive ball arrangedto roll upon said resistance element, a flexible insulating diaphragm overlaying said groove and sealing said groove, a flexible electro-conductive tape afiixed to said diaphragm on the groove 'side of said diaphragm, overlaying but spaced from said resistance element,-said tape bending coincidentally with bending of said diaphragm, electrical connections to said resistance element and to said tape, an arm mounted on said housing means for movement of its free end parallel to said resistance element, and a member'mounted on the 'free end of said arm pressing on said diaphragm to flex said diaphragm and engaging said ball through said diaphragm so as to cause said ball to follow movements of said arm, said ball then rolling between said resistance element and said tape as a conductor therebetween.

5. A variable resistor comprising housing means, a resistance element carried by said housing means, an elec- "tro-conductive ball arranged to roll upon said resistance element, a flexible insulating diaphragm over-laying said housing means and said ball, a flexible electro-conduc-tive tape aflixed to the side of said diaphragm adjacent said ball, said tape and said diaphragm being bendable in unison, electrical connections to said resistance element and to said tape, an arm mounted on said housing means for movement of its free end over said diaphragm, and a substantially annular flange carried by the free end of said arm and defining a central cavity into which said ball fits,

"said flange pressing said diaphragm and said tape to form v a pocket containing said ball, said ball moving relatively to said resistance element in response to movement of said flange. I 1

6. A variable resistor comprising housing means, a resistance element carried by said housing means, a flexible diaphragm overlaying said resistance element and spaced therefrom, an electro-conductive ball mounted for rolling between said resistance element and said diaphragm, an

7. A variable resistor which includes: a housing; a resistance element carried by said housing; a flexible diaphragm having edges, the edges of said flexible diaphragm being secured to said housing so as to define an enclosed area surrounding said resistance element; an electrical return mounted within said enclosed area adjacent to and spaced from said resistance element; contact means capaarm mounted on said housing means for movement of its free end over said diaphragm on the side of said diaphragm opposite to said ball and parallel to said resistance element, a flange on the free end of said arm defining a cavity Within said flange, said flange pressing said diaphragm upon said ball to form a pocket confining said ball, an electric circuit connected to said resistance element, and a second'electrical circuit including a flexible electro-conductive tape carried by said diaphragm between said diaphragm and said ball, said ball engaging said tape.

ble of simultaneously engaging said electrical return; means and said resistance element and capable of being moved with respect to said electrical return means and said resistance element mounted Within said enclosed area adjacent to said diaphragm; means for moving said contact means along said resistance element and said electrical return engaging said diaphragm and disposed on the side of said diaphragm remote from said enclosed area so as to deformsaid diaphragnrinto engagement with said contact means and moving along with said contact means. i

8. A variable resistor which includes: ahousing; a resistance element carried by said housing; a flexible diaphragm having edges, the edges of said flexible diaphragm being secured to said housing so as to define an enclosed area surrounding said resistance element; an electrical return mounted within said enclosed area adjacent to and spaced from said resistance element; contact means capable of simultaneously engaging said electrical return means and said resistance element and capable of being moved with respect to saidelectri-cal return means and said resistance element mounted within said enclosed area adjacent to said diaphragm; means for moving said contact means along said resistance element and said electrical return engaging said diaphragm and disposed on the side of said diaphragm remote from said enclosed area so as to deiorm said diaphragm into engagement With said contact means and moving along With said contact means;

and an electrical non-conductive fluid filling said area between said housing and said diaphragm.

References Cited in the file of this patent v I UNITED STATES PATENTS 1,064,722 

1. A VARIABLE RESISTOR COMPRISING HOUSING MEANS, A RESISTANCE ELEMENT CARRIED BY SAID HOUSING MEANS, A FLEXIBLE DIAPHRAGM ATTACHED TO SAID HOUSING MEANS OVERLAYING SAID RESISTANCE ELEMENT AND SPACED THEREFROM SO AS TO ENCLOSE SAID RESISTANCE ELEMENT, AN ELECTRO-CONDUCTIVE BALL MOUNTED FOR ROLLING BETWEEN SAID RESISTANCE ELEMENT AND SAID DIAPHRAGM, AN ARM MOUNTED ON SAID HOUSING MEANS FOR MOVEMENT OF ITS FREE END OVER SAID DIAPHRAGM ON THE SIDE OF SAID DIAPHRAGM OPPOSITE TO SAID BALL AND PARALLEL TO SAID RESISTANCE ELEMENT, A FLANGE ON THE FREE END OF SAID ARM DEFINING A CAVITY WITHIN SAID FLANGE, SAID FLANGE PRESSING SAID DIAPHRAGM UPON SAID BALL TO FORM A POCKET CONFINING SAID BALL WHEREBY UPON MOVEMENT OF SAID ARM SAID BALL AND ARM ARE CONSTRAINED TO MOVE AS A UNIT HAVING RELATIVE MOTION WITH RESPECT TO SAID RESISTANCE ELEMENT AND SAID DIAPHRAGM, AN ELECTRIC CIRCUIT CONNECTED TO SAID RESISTANCE ELEMENT, AND A SECOND ELECTRIC CIRCUIT WITH WHICH SAID BALL IS IN CIRCUIT. 